Thursday, 26 May 2016

During the 1990s, groundbreaking work by psychologists demonstrated that human memory is flexible and vulnerable and that it’s very easy for people to experience “false memories” that feel real, but which are actually a fiction. One major implication of this was in the evaluation of adults’ accounts of how they’d been abused in childhood. In a recent journal editorial, for instance, one of the pioneers of false memory research argued that the same techniques used by therapists to recover repressed memories of abuse have been shown in the lab to “produce false memories in substantial numbers of research participants”.

But there are some experts who believe the false memory researchers have gone too far. Chris Brewin and Bernice Andrews are two British psychologists with these concerns. In their new systematic review in Applied Cognitive Psychology they have taken a hard look at all the evidence, and they argue that we need to rethink the idea that false memories are so easily induced.

Key to this reevaluation is the question of what exactly is a false memory. It seems fair to require that it involves a person recollecting an experience, including sensory details, and believing confidently that this is a memory (rather than a dream or imagining) of something that really happened. But studies in this area that involve inducing false memories often adopt a more liberal definition, such as a subtle shift in a person’s willingness to believe that a given event described to them could possibly have happened in their childhood.

Consider one key experimental technique known as “imagination inflation”, which aims to provoke false memories in participants simply by asking them to write about fictitious events as if they had really happened.

As a first step participants are surveyed about a range of things that might happen in a typical childhood, and then they are asked to use their imagination to write about one of these events that they believe didn’t actually happen in their own childhood. After this writing task, participants are asked again to rate how likely it is that they actually experienced this event in their own childhood.

Overall, after completing the imaginative writing task, most people tend to shift their beliefs, to think that it’s more plausible that they may actually have experienced the event they wrote about. But in 13 of 14 the published datasets that Brewin and Andrews reviewed where this technique was used, belief only changed by one point or less on an eight-point scale (from strongly believing it didn’t happen on one end of the scale, to strongly believing it did on the other). As these shifts in belief often weren’t enough to tip participants over the scale’s half-way point, this supposed induction of "false memories" involved the sowing of doubt but not the creation of a new memory – most participants still considered that the events they’d written about hadn’t happen to them, it’s just that they were less confident in that belief.

Another issue with these research paradigms is that, especially for studies that provided fairly general childhood events (e.g. "you gave someone a gift for no special reason"), the imagination writing task may actually have triggered genuine memories that didn’t pop up the first time around, which are then misclassified by researchers as false.

Another technique to induce false memories is to use an authority figure, such as a therapist, to apply social pressure to a participant that an event was likely to have happened in their childhood. There are problems with this method too. Again, the data mostly involve participants’ increased belief in the possibility of a past event having occurred, rather than any changes in their recollection per se. Again, in 14 of 15 previously published datasets, belief did not shift beyond the midpoint.

Looking at only the most susceptible participants, in some cases there were strong changes in belief, but these tended to be for low-intensity events, such as eating and disliking a particular foodstuff; for more specific events, beliefs were less committed.

Five previously published datasets also looked at actual changes in remembering. At the high end, new recollection (after hearing testimony from an authority figure that an event had occurred in the participants' childhood) was seen in around 30 per cent of the sample – again for fictitious food-related events – but at the lowest end, just two per cent of participants reported new recollections.

The most powerful technique used to induce false memories is memory implantation. This approach involves parents and authority figures conniving over multiple sessions to persuade a participant that an event really happened in their childhood, going as far in some cases as doctoring photographs to produce incontrovertible proof. These studies often produce new recollections of some kind – up to 78 per cent of participants report new, false memories when doctored photographs are used – but Brewin and Andrews show that when an even more stringent definition of a false memory is used – that it must involve mental images – then this rate of new recollection drops to 25 per cent, and regarding memories that the participant is actually confident in, to only 15 per cent.

Overwhelmingly, most participants in these studies disbelieve the childhood event ever happened, and they doubt any apparently new memories that arise, despite the pressure to think otherwise. Tellingly, when studies have collected ratings of the strength of any new memories from both the participants and the researchers, the researchers’ ratings are routinely higher. After hearing their parents’ stories, the participants typically become better able to narrate a plausible and even elaborate account that persuades the researcher a memory has been created. But often the participants themselves aren't buying it, and they can draw the distinction between memory-like content and a true memory.

It’s clear that false memory paradigms can shift how we evaluate past events, and can for a minority of participants provoke memory-like experiences. But the rates are very low and the effects variable, and the one that produces the strongest effect – memory implantation – is also the most invasive, and least likely to match the experiences of people in normal life or within a therapy session. Brewin and Andrews suggest their review “indicates that the majority of participants are resistant to the suggestions they are given” and that the rhetoric that false beliefs are easy to instil should be re-examined.